During hydrocarbon drilling operations, it may become necessary to permanently or temporarily seal off a portion or various zones of a wellbore. Plugs are tools that are typically lowered into a cased hydrocarbon well and provide a seal to isolate two zones in the well when set in position inside the casing. Retrievable plugs provide temporary sealing and separation of zones during drilling and workover operations. Typically, conventional retrievable plugs are characterized by anchoring elements, such as conventional slips, and also generally include one of a variety of conventional rubber seal or packing elements.
The anchoring elements are used to grip the inside surface of the well casing to prevent the set plug from moving within the casing. The seal or packing elements also engage the inside surface of the well casing to seal the annulus between the plug and well casing. A retrievable plug is removed from the well casing through the release and retraction of the anchoring elements and sealing or packing elements after the shear member is activated.
Typically, retrievable plugs are designed for use with a range of large diameter casing tubing sizes. In some instances, a plug may be desired to seal sections of coil tubing, wherein the coil tubing may or may not include a longitudinal seam along the tubing inner surface. However, in coil tubing applications, where the tubing diameters can be smaller and the plugs are typically deployed at the bottom of the tubing, retrievable plugs have not been consistently utilized, especially where the coil tubing is characterized by a seam along the inner wall of the coil tubing. The presence of an inner wall seam spanning the length of the coil tubing makes it difficult to properly orient the plug and as a result to completely seal the annulus between the plug and coil tubing. Also, the presence of the inner wall seam makes retrieving the plug difficult and economically inefficient.
Accordingly, there remains a need to develop new and improved systems and apparatus for a retrievable plug disposed in coil tubing near the surface that address certain of the foregoing difficulties.